The subsea production tree is an arrangement of valves, pipes, fittings and connections placed on top of a wellbore. Orientation of the valves can be in the vertical bore or horizontal outlet of the tree as shown in the figure. The valves can be operated by electrical or hydraulic signals or manually by a diver or ROV (remote operated vehicle). In addition to the valves arrangement one of the major difference between a horizontal and a vertical tree is the position in which the tubing hanger sits. In a horizontal tree the tubing hanger is located in the tree body which make it impossible to retrieve the tree without pulling out the completion, this kind of configuration is suitable for wells in complex reservoirs that requires frequent intervention and workovers. On the other side, in a vertical tree the tubing hanger is located inside the wellhead making it possible to retrieve the tree without pulling the completion out, this is a simpler, cheaper and it is suited for normal operations.
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